Retractor with pretensioner

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation-in-part of corresponding U.S. patent application Ser. No. 10/968,504, filed Oct. 19, 2004 now U.S. Pat. No. 7,318,607, and is also a continuation-in-part of corresponding U.S. patent application Ser. No. 11/115,583, filed Apr. 27, 2005. All of the foregoing applications are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to seat belt restraint apparatus for restraining an occupant of an automobile, and more particularly relates to a retractor having a pretensioner for controlling load limitation aspects of the restraint system.

BACKGROUND OF THE INVENTION

Seat belt restraint systems for automobiles often include a pretensioner which is structured to apply tension to the seat belt when an impact event such as an accident situation is detected. When the pretensioner is activated, the pretensioner eliminates any slack in the seat belt, and thus controls the physical space between the occupant and the seat belt. In this manner, the occupant of the seat is coupled with the seat belt as the occupant initially moves forward relative to the seat, thereby controllably restraining the occupant, reducing occupant excursion, and preventing undue loads when the occupant moves forwardly into the seat belt.

A retractor is another standard component of a seat belt restraint system which includes a spool receiving the webbing material of the seat belt. The spool is used to wind up and store the webbing. Generally, the spool is locked in place upon detection at an impact situation in order to restrain the occupant via the seat belt. Recently, retractors have been designed having one or more force limiting elements which are structured to allow the spool to rotate and pay out the webbing material of the seat belt upon reaching predetermined force levels between the occupant and seat belt. In this manner, the restraint force imposed on the occupant can be limited in a controlled manner, thereby providing a certain load limitation characteristics.

Despite these and other improvements to automobile restraint systems, there remains a need to provide a retractor that includes a pretensioner while providing increased control and variation over the load limitation characteristics of the retractor system.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a retractor having a pretensioner that provides increased control and variation over the load limitation characteristics of the retractor system. The retractor generally includes a spool receiving a portion of the seat belt wound thereon, which is rotatable to retract or pay out the seat belt. A first force limiting element is connected to the spool, and a locking mechanism is operatively connected to the spool through the first force limiting element to prevent paying out of seat belt, such as during an impact event. However, the first force limiting element provides some limited paying out of the seat belt in order to control the belt forces imposed on the occupant. A second force limiting element is connected to the spool. The pretensioner has a drive mechanism operatively connected to the spool through the second force limiting element. A selectively actuatable clutch is positioned between the second force limiting element and one of the spool or the drive mechanism. The selectively actuatable clutch controls force transmission between the spool and the drive mechanism, thereby providing greater control over the load limitation characteristics of the retractor.

According to more detailed aspects, the selectively actuatable clutch includes an initial position and an activated position, wherein the initial position couples the drive mechanism and the spool for force transmission, and the activated position decouples the drive mechanism and the spool. The clutch may further include a deactivated position that again couples the drive mechanism in the spool. The selectively actuatable clutch preferably includes a clutch driving mechanism having a pyrotechnic charge. The retractor may further include a second selectively actuable clutch, one being positioned between the second force limiting element and the spool, the other being positioned between the second force limiting element and the drive mechanism. In this case, one of the clutches has an initial position decoupling the drive mechanism or spool from the second force limiting element, while the other clutch has an initial position coupling the drive mechanism or spool and the second force limiting element.

According to another embodiment of the present invention, a method is provided for restraining an occupant of an automobile. The method includes providing a retractor having a pretensioner, a spool, a first force limiting element, a second force limiting element and a locking mechanism, preferably constructed as described above. A selectively actuatable clutch is provided interposed between the second force limiting element and one of the drive mechanism or the spool. The method includes switching the clutch drive mechanism to an activated position decoupling the second force limiting element to one of the drive mechanism and the spool. According to more detailed aspects the switching step occurs on detection on an impact event. The method may further include switching the clutch drive mechanism to a deactivated position coupling the second force limiting element from one of the drive mechanism or the spool. Further, the drive mechanism of the pretensioner may be activated upon detection of an impact event to attract seat belt onto the spool, and the drive mechanism may be blocked throughout the impact event to provide load limitation via the second force limiting element.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:

<figref idref="DRAWINGS">FIG. 1</figref> is a cross-sectional view of a retractor constructed in accordance with the teachings of the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is another cross-sectional view of the retractor depicted in <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a graph depicting the belt load over time in the retractor of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 4</figref> is another graph depicting the belt load over time in the retractor of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional view of another embodiment of a retractor constructed in accordance with the teachings of the present invention;

<figref idref="DRAWINGS">FIG. 6</figref> is another cross-sectional view of the retractor depicted in <figref idref="DRAWINGS">FIG. 5</figref>; and

<figref idref="DRAWINGS">FIG. 7</figref> is a side view, partly in cross-section, depicting the retractor of <figref idref="DRAWINGS">FIG. 5</figref>.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the figures, <figref idref="DRAWINGS">FIG. 1</figref> depicts a cross-sectional view of a retractor <b>20</b> constructed in accordance with the teachings of the present invention. The retractor <b>20</b> is adapted for an automobile having a seat belt <b>22</b> restraining an occupant (not shown). As is known in the art, the vehicle includes an impact sensor <b>24</b> sending a signal <b>26</b> indicative of an impact event such as a crash event. Any impact sensor that is or will be known to those skilled in the art may be readily employed in conjunction with the retractor <b>20</b> of the present invention. An electronic control unit <b>28</b> such as a central processing unit (CPU) or other controller receives the signal <b>26</b> and controls the vehicle's response to the same.

As is known in the art, during normal use the retractor <b>20</b> is used to wind up the seat belt <b>22</b> about a spool <b>30</b> which is rotatably mounted to a frame <b>32</b> of the retractor <b>20</b>. The spool <b>30</b> is coupled to a first force limiting element <b>34</b>, which preferably comprises a torsion rod or torque bar, as is also known in the art. It will be recognized that other types of force limiting elements other than torsion rods may be employed in conjunction with the present invention, including sleeves, rings or tubes. The first force limiting element <b>34</b> generally includes a first end <b>36</b> and a second end <b>38</b>. The first end <b>36</b> is connected to the spool <b>30</b> via a coupling <b>40</b>, while the second end <b>38</b> is connected to a profiled head <b>44</b> via another coupling <b>42</b>. Preferably, the coupling <b>40</b> is constructed as a low-profile spline as disclosed in U.S. patent application Ser. No. 11/008,308 filed Dec. 9, 2004, the disclosure of which is incorporated herein by reference in its entirety.

The retractor <b>20</b> further includes an end assembly <b>46</b> which includes a locking mechanism that selectively engages the profiled head <b>44</b> and second end <b>38</b> of torsion bar <b>34</b> during an impact event such as a vehicle collision, providing an “emergency locking retractor” function as is well known in the art. For example, end assembly <b>46</b> is of the type disclosed in U.S. Pat. Nos. 6,616,081; 6,012,667; and 5,924,641, the disclosures of which are hereby incorporated by reference in their entirety. Through blocking of the profiled head <b>44</b>, the spool <b>30</b> is prevented from rotating and the occupant is restrained by the seat belt <b>22</b>. However, the retractor <b>20</b> and first force limiting element <b>34</b> also provide a low load limitation function in order to limit the restraint force imposed on the occupant. Upon reaching a predetermined restraint force, the spool <b>30</b> will begin to rotate and “pay out” the seat belt <b>22</b> by actuation of the first force limiting element <b>34</b>. That is, upon reaching a predetermined force, the torsion rod <b>36</b> will twist to allow some rotation of the spool <b>30</b> (as well as coupling <b>40</b> and first end <b>36</b>) relative to the profiled head <b>44</b> (and hence relative to coupling <b>42</b> and second end <b>38</b>) which is fixed by the locking mechanism of end assembly <b>46</b>. In this manner, a low load limitation characteristic is provided by the torsion of the first force limiting element <b>34</b> to allow limited pay out of the seat belt <b>22</b> wound on the spool <b>30</b>.

Also shown in <figref idref="DRAWINGS">FIG. 1</figref>, the retractor <b>20</b> includes a pretensioner <b>50</b> for pretensioning the seat belt <b>22</b> through the retractor <b>20</b>. The pretensioner <b>50</b> is activated by the electronic control unit <b>28</b> via a pretension signal <b>48</b>. In particular, a drive mechanism <b>52</b> is actuated to effectuate rotation of the spool <b>30</b> via a second force limiting element <b>54</b>. A first end <b>56</b> of the second force limiting element <b>54</b> is connected to the spool <b>38</b> via the shared coupling <b>40</b>, although it will be recognized that the first end <b>56</b> may be directly attached to the spool <b>30</b> or include its own coupling. The drive mechanism <b>52</b> of the pretensioner <b>50</b> is connected to the second end <b>58</b> of the second force limiting element <b>54</b> by way of a clutch <b>60</b> and a coupling <b>62</b> at the second end <b>58</b> of the second force limiting element. Preferably, the drive mechanism <b>52</b> is initially disengaged from the pinion <b>64</b> so that the spool <b>130</b> may freely rotate during normal operation of the retractor <b>20</b>. As is known, upon activation of the pretensioner <b>50</b>, the drive mechanism <b>52</b> engages the pinion <b>64</b> for transmitting force therebetween.

The drive mechanism <b>52</b> may take many forms, such as an electric motor or pyrotechnic drive,. One exemplary pretensioner having a pyrotechnic drive is disclosed in U.S. Patent No. 5,881,962, the disclosure of which is incorporated by reference herein in its entirety. Upon detection of an impact event, the drive mechanism <b>52</b> is activated and engages the pinion <b>64</b>, which in turn operates through the clutch <b>60</b> and the second force limiting element <b>54</b> to rotate the spool <b>30</b> and retract seat belt onto the spool <b>30</b>. That is, the seat belt is pretensioned to remove any slack between the seat belt <b>22</b> and the occupant. Then, the drive mechanism <b>52</b> of the pretensioner <b>50</b> is blocked in order to block further rotation of the spool <b>30</b>, including protraction or “paying out” of the seat belt. The pretensioner <b>50</b> may be blocked by maintaining the pressure of the pyrotechnic charge, and/or by a separate blocking element, such as is disclosed in U.S. patent application No. 11/222,411, filed on Sep. 08, 2005, the disclosure of which is incorporated herein by reference in its entirety.

At about the same time as the blocking of the pretensioner <b>50</b>, the profiled head <b>44</b> is blocked by the locking mechanism. Thus, through activation of the pretensioner <b>50</b>, rotation of the spool <b>30</b> is blocked through both the first and second load limiting elements <b>34</b>, <b>54</b>, providing a high load limitation function to control the restraint force imposed on the occupant.

For increased control over the level of load limitation provided by the retractor <b>20</b>, the clutch <b>60</b> is constructed to permit selective connection of the pretensioner <b>50</b> and its pretensioner drive <b>52</b> to the second force limiting element <b>54</b> and spool <b>30</b>. More specifically, the initial position of the clutch <b>60</b> connects the pretensioner <b>50</b> to the spool <b>30</b> for pretensioning of the seat belt <b>22</b> and high load limitation through blocking of the pretensioner <b>50</b>, as described above. The activated position of the clutch <b>60</b> decouples the pretensioner <b>50</b> and spool <b>30</b>, as will be described below. Generally, the CPU <b>28</b> will generate a clutch signal <b>66</b> to decouple the pretensioner <b>50</b>, based on such factors as occupant type or size (i.e. 5^thpercentile occupant), crash severity or type of impact event, and the firing of other passive restraints such as air bags or other restraint apparatus.

Upon receiving a clutch signal <b>66</b> from the CPU <b>28</b>, a clutch drive <b>61</b> includes pyrotechnic charge <b>68</b> or other combustible material that is ignited inside a combustion chamber <b>70</b>. The pressure in the chamber <b>70</b> presses on a driving element <b>72</b> which engages a hub <b>74</b>. As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the hub <b>74</b> is interposed between the pinion <b>64</b> of the drive mechanism <b>52</b> and the coupling <b>62</b> of the second force limiting element <b>54</b>. The hub <b>74</b> includes a tongue <b>76</b> received in a groove <b>78</b> of the pinion <b>64</b>, thereby rotatably coupling the two pieces. Similarly, the hub <b>74</b> includes at least one shank <b>80</b> projecting radially inwardly for engagement with a shoulder <b>82</b> of the coupling <b>62</b>. As best seen in <figref idref="DRAWINGS">FIG. 1</figref>, upon axial translation of the hub <b>74</b> by the driving element <b>72</b>, the hub <b>74</b> may be positioned in and out of engagement with the coupling <b>62</b> of the second force limiting element <b>54</b>.

Further, the clutch <b>60</b> includes a spring <b>84</b> or other resilient member biasing the hub <b>72</b> into a position engaged with the coupling <b>62</b>. As such, the clutch <b>60</b> includes an initial position where the pretensioner drive mechanism <b>52</b> is operatively coupled to the second force limiting element <b>54</b> and spool <b>30</b>. In an activated position, the hub <b>74</b> is driven such that the clutch <b>60</b> operatively decouples the drive mechanism <b>52</b> and the spool <b>30</b> via the second force limiting element <b>54</b>. Finally, it can also be seen in <figref idref="DRAWINGS">FIG. 1</figref> that the clutch <b>60</b> includes a relief valve <b>86</b> coupled to the combustion chamber <b>70</b>. As such, pressure within the chamber <b>70</b> may be selectively released (such as via another clutch signal <b>66</b> or other direct signal) and the hub <b>74</b> retracted axially, thereby providing a deactivated position where the drive mechanism <b>52</b> is again coupled to the second force limiting element <b>54</b> and spool <b>30</b>.

The load limitation characteristics provided by the retractor <b>20</b> and pretensioner <b>50</b>, as controlled through the clutch <b>60</b> will now be described with reference to the graphs depicted in <figref idref="DRAWINGS">FIGS. 3 and 4</figref> which present idealized data. In the figures, the Y-axis represents belt load while the X-axis represents time. Upon detection of an impact event, the CPU <b>28</b> will send a pretensioning signal <b>48</b> to the pretensioner <b>50</b> to initiate its drive mechanism <b>52</b>. The pretensioner drive mechanism <b>52</b> rotates the spool <b>30</b> via the second force limiting element <b>54</b> until the pretensioner <b>50</b> is blocked. At about the same time, the pretensioner <b>50</b> is blocked, the profiled head <b>44</b> blocks the second end <b>38</b> of the first load limiting element <b>34</b>, and rotation of the spool <b>30</b> is prevented except through the controlled rotation provided by the first and second force limiting elements <b>34</b>, <b>54</b>. As such, the load limitation provided by the first and second force limiting elements <b>34</b>, <b>54</b> are superimposed to provide a high load limitation characteristic depicted as line <b>92</b> in <figref idref="DRAWINGS">FIG. 3</figref>. At any point during the impact event (such as points <b>94</b>, <b>94</b><i>b</i>, <b>94</b><i>c</i>, <b>94</b><i>d</i>), the CPU <b>28</b> may determine that a lower load limitation level is desired, and thus send the clutch signal <b>66</b> to activate the clutch <b>60</b>. As previously discussed, in the activated position the clutch <b>60</b> decouples the pretensioner drive mechanism <b>52</b> from the second force limiting element <b>54</b> and spindle <b>30</b>. In this activated position of the clutch <b>60</b>, the load limitation is provided solely through the first load limiting element <b>34</b>, which provides a low load limitation characteristic, indicated by line <b>90</b>. Similarly, if at some point <b>96</b><i>a</i>, <b>96</b><i>b </i>CPU <b>28</b> determines higher load limitation is desired, a clutch signal <b>66</b> may again be sent to deactivate the clutch through the relieving pressure in the chamber <b>70</b> via relief valve <b>86</b>.

It will also be recognized by those skilled in the art that the initial, activated and deactivated positions of the clutch <b>60</b> may be reversed, as will be described with reference to <figref idref="DRAWINGS">FIG. 4</figref>. For example, if the shoulders <b>82</b> of the coupling <b>62</b> were moved to the left side of the coupling <b>62</b> in <figref idref="DRAWINGS">FIG. 1</figref>, such that the hub <b>74</b> is not initially in engagement with the shoulders <b>82</b> of coupling <b>62</b>, the initial position of the clutch <b>60</b> would be to decouple the pretensioner drive mechanism <b>52</b> and the second force limiting element <b>52</b>, <b>54</b>. Thus, upon activation of this reversed clutch mechanism <b>60</b>, the pretensioner drive mechanism <b>52</b> would be coupled to the spool <b>30</b> via the second force limiting element <b>54</b>, and upon deactivation of the clutch <b>60</b> the drive <b>52</b> and spool <b>30</b> would again be decoupled. As such, when an impact event is detected and the CPU <b>28</b> decides not to fire the pretensioner <b>50</b>, the profiled head <b>44</b> may be locked to provide a low load limitation characteristic <b>90</b>. Then, the CPU <b>28</b> could initiate the pretensioner drive mechanism <b>52</b>, and when the pretensioner <b>50</b> is blocked, activate the clutch <b>60</b> to provide load limitation through both the first and second load limiting elements <b>34</b>, <b>54</b>. Thus, at any point <b>94</b><i>a</i>, <b>94</b><i>b</i>, <b>94</b><i>c </i>in time the retractor <b>20</b> can be switched to a high load limitation characteristic as indicated by line <b>92</b>. Finally, the clutch <b>60</b> could then be deactivated at another point in time <b>96</b><i>a</i>, <b>96</b><i>b </i>in order to return to low load limitation <b>90</b> through the first force limiting element <b>34</b>.

Turning now to <figref idref="DRAWINGS">FIGS. 5</figref>, <b>6</b> and <b>7</b>, another embodiment of the retractor <b>120</b> having a pretensioner <b>150</b> has been depicted in accordance with the teachings of the present invention. Generally, the retractor <b>120</b> and the pretensioner <b>150</b> with its drive <b>152</b> are of a substantially similar construction as the prior embodiment described with reference to <figref idref="DRAWINGS">FIGS. 1-4</figref>. In this embodiment, however, the clutch mechanism <b>160</b> is provided between the second force limiting element <b>154</b> and the spool <b>130</b>. As in the prior embodiment, the spool <b>130</b> is rotatably mounted and is coupled to a first load limiting element <b>134</b> via a coupling <b>140</b>. Here, the second force limiting element <b>154</b> does not share the coupling <b>140</b>, but rather includes its own coupling <b>163</b> at its first end <b>156</b>. As best seen in <figref idref="DRAWINGS">FIG. 6</figref>, the coupling <b>163</b> defines a pair of shoulders <b>165</b> which are sized to receive a pair of coupling pawls <b>167</b>. The pawls <b>167</b> are pivotally mounted to the spool <b>130</b> for rotation in and out of engagement with the shoulders <b>165</b>. Engagement of the pawls <b>167</b> with the shoulders <b>165</b> is maintained by the provision of a spool ring <b>166</b> that is axially translatable. In <figref idref="DRAWINGS">FIG. 5</figref>, the spool ring <b>166</b> has been shown in the engaged position, wherein a pair of tabs <b>169</b> project radially inwardly to prevent rotation of the coupling pawls <b>167</b> and force engagement with the coupling <b>163</b> of the second force limiting element <b>154</b>. Thus, in this initial position shown in <figref idref="DRAWINGS">FIGS. 5 and 6</figref>, force transmission from the second load limiting element <b>154</b> to the spool <b>130</b> is provided through the clutch <b>160</b>.

As best seen in <figref idref="DRAWINGS">FIG. 7</figref>, axial translation of the spool ring <b>166</b> is effected through a set collar <b>172</b> which is arranged in the frame <b>132</b> of the retractor <b>120</b>. The clutch <b>160</b> includes a drive <b>161</b> having a pyrotechnic charge <b>168</b> that impacts a piston <b>170</b> causing its linear movement. In its linear movement, the piston <b>170</b> acts on a shoulder <b>171</b> projecting radially from the set collar <b>172</b>, such that the set collar <b>172</b> is caused to rotate when the piston <b>170</b> is actuated. The set collar <b>172</b> is connected to the frame <b>132</b> such that it does not rotate during the normal function of the spool <b>130</b>, but can perform a limited rotational movement during its adjusting motion. Particularly, the set collar <b>172</b> is supported against the frame <b>132</b> by inclined ramps (not shown) such that through rotation of the set collar <b>172</b> axial displacement occurs, thereby forcing axial displacement of the spool ring <b>166</b> by virtue of their adjacent position.

Another embodiment of the retractor <b>20</b>, <b>120</b> could employ multiple clutches, such as both clutch <b>60</b> and clutch <b>160</b> previously described. In this case, the pretensioner drive <b>52</b>, <b>152</b> can be initially engaged with the pinion <b>64</b>, <b>164</b>, which would occur at about the same time as the actuation of the pretensioner <b>50</b>, <b>150</b> to force transmission.

It will be recognized by those skilled in the art that the retractor <b>20</b> of the present invention provides increase adaptability and control over the load limitation characteristics imposed by the retractor and seat belt on an occupant, by providing additional load limitation through a second force limiting element and activation of the pretensioner which can be selectively controlled via the clutch <b>60</b>. Further, the retractor <b>20</b> reduces or eliminates “locking dip”, which as used in the industry describes the phenomena of loss of belt load when the torque load is transferred from the pretensioner to the blocking element which blocks the profiled head to activate the force limiting element. By activating the pretensioner, and maintaining the activation of the second force limiting element while the first force limiting element is activated through blocking of the tread head, “locking dip” is substantially eliminated.

The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. For example, it will be recognized by those skilled in the art that while the first ends <b>36</b>, <b>56</b> of the first and second force limiting elements <b>34</b>, <b>54</b> are located adjacent each other and are rigidly connected to the spool <b>30</b>, the second force limiting element <b>54</b> and the pretensioner <b>50</b> could be connected to the second end <b>38</b> of the first force loading element <b>34</b>, and more specifically connected to the profiled head <b>44</b>. It will also be recognized that the first and second load limiting elements <b>34</b>, <b>54</b> may be formed out of a single torsion bar wherein the opposing free ends of the bar would be selectively blocked (either via the locking mechanism or the pretensioner drive <b>52</b>) to cause load limitation through the force limiting elements <b>34</b>, <b>54</b>. Further, the second force limiting element <b>54</b> could be a hollow tube which slides around a reduced diameter end of the torsion rod <b>34</b> forming the first force limiting element <b>34</b>.

Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.